If you are on such a tight budget you cannot even afford a donation, how will you afford vet bills if the pet is ill?
Besides, a rescue pet has been seen by a vet, it had its shots, is usually chipped and, if old enough, has been neutered.
Just figure out what that would cost you if you pick up a 'free puppy'or kitten.
Besides, animals are not goods, so they should not be traded or given away on internetsites intended for trading and swapping.
Having a pet - and deciding where to get it - should be a well-considered decision, and these sites are often used by people who are breeding (often inbreeding) for profit, and by people trying to get rid of unwanted or unintended litters.
We have a similar site in the Netherlands called Marktplaats (market place), and they do allow ads for pets.
Many of the pets advertized are bred commercially under very bad circumstances. People get a puppy or kitten supposedly from a one-off litter raised in the family home, and in truth they get sickly inbred pets kept in a shed or attic, who are allowed into the house only when prospective buyers come around.
And there are people who simply buy or collect a pet on impulse and dump it on the same site within days or weeks.
My friend once saw a lovely kitten on this marktplaats, but when she tried to phone the owner, the kitten had just been given to someone. The very next day it was offered on marktplaats again, this time by the new owner. The very same kitten, within 24 hours. He 'didn't get along' with the other cat.
We went there at once and collected it, it was a long drive, but I am glad we got him away. The cats got on perfectly, just some mild hissing every now and then, but they were both sleeping in hte same room when we arrived and were totally relaxed. The first day, two cats who had not even been properly introduced, just thrown together in the living room, that was wonderful. But these people didn't know anything about cats, even though they had had the other cat for some time. so they just dumped the kitten again. Not a single question about housing, experience with cats, nothing. You want it? It's yours.
The kitten has been with my friend for over 5 years now, and he is super.
But these things happen if you can pick up a kitten the way you pick up a second hand book, on impulse. If it turns out to be no good, you just dump it again.